The present invention relates to an image reading apparatus with an automatic document feeder apparatus (ADF) and an image reading method for reading an original transported to a platen. More particularly, the present invention relates to an image reading apparatus and an image reading method that determine whether an original to be read includes black and white images or color images, and read the images on the original according to a result of the determination.
In recent years, a computer, the Internet and electronic photos are widely used to handle color images. Accordingly, there has been an increasing demand for copying, printing, and transmitting the color images because of the superior quality as opposed to black and white images. For that reason, an image reading apparatus has been required to quickly read a color original with high quality.
However, when an image reading apparatus reads a color original, it is normally necessary to read image data for each of the three primary colors, namely red (R), green (G) and blue (B). Thus, when reading a color original with the same resolution as that of a black and white original, the image reading apparatus has to read at a speed than slower for reading a black and white original.
An image reading apparatus may read a set of originals including both color originals and black and white originals. When the apparatus reads such a set of originals in a color reading mode, a speed of reading the black and white originals will be dramatically slowed.
To solve this problem, a conventional apparatus pre-scans an original to determine whether the original has a black and white image or color image. Then, when the original has only a black and white image, the image reading apparatus reads at a comparatively high speed in a black and white mode. Conversely, when he original has a color image, the image reading apparatus uses the color reading mode with a slower speed. This system is known as the ‘pre-scan/actual scan method’.
In Japanese Patent Publication (Kokai) No. 09-261417, an image processing apparatus has been disclosed as a modified version of the ‘pre-scan/actual scan method’. The reading apparatus is provided with a re-circulating document feeder. It is determined if the original has a black and white image or color image for all documents on the document tray through a process of transporting the originals through a reading position inside the apparatus. Then, the apparatus stores a result for each page of the originals stacked on the original tray. Next, for the actual reading, the originals are returned to the original tray and sequentially fed in the same order. Then, the determination result is retrieved for each original, and the originals are read according to the results based on whether the original has a black and white image or color image.
An image reading apparatus disclosed in U.S. Pat. No. 5,946,527 also employs the pre-scan/actual scan method to determine whether a original is in black and white or in color by reading the original in the process to pass the original on an original tray through a reading position. Then, the original is read again according to a result of the determination.
In the image reading apparatus, it is determined whether the original fed from the original tray includes a black and white image or color image when the original passes through the reading position on the platen. In the image reading apparatus, it is possible to rotate discharge rollers in both directions for discharging the original to the discharge tray. Thus, it is possible to reverse and transport the original to the reading position again, so that both sides of the original can be placed on the reading position.
Therefore, when the original passes through the reading position for the first time, the apparatus determines whether the original has a black and white image or color image. After a leading edge of the original is discharged to the discharge tray, the discharge rollers are rotated in reverse to switchback the original. The original is turned over front to back, so when passing through the reading position for the second time, the apparatus does not read the original. After the original is switched back again on the discharge tray, when the original passes through the reading position for the third time, the image thereupon is read according to the result obtained when the original passes through the reading position for the first time. While the apparatus stores the image data, the original is discharged to the discharge tray.
Also, Japanese Patent Publication (Kokai) No. 11-2931 has disclosed an apparatus in which a set of originals having differing sizes is placed on the original tray. The original passes through a reading position to determine a size of the original, and is subsequently sent to the discharge tray. The original is transported to the reading position again for reading. This apparatus employs a transport mechanism for determining the size of the original. It may be possible to determine whether an original has a black and white image or color image if a reading device such as a CCD is installed at a position where the original size detection sensors are arranged in the transport mechanism.
In the image reading apparatus with the pre-scan/actual scan method described above, the original is transported through the same path when the original is read with only the actual scan and the original is read with both the pre-scan and the actual scan. Therefore, it is difficult to reduce a processing time when the image reading apparatus with the pre-scan/actual scan method reads a set of originals including both black and white originals and color originals.
In addition to the problems described above, the apparatus disclosed in Japanese Patent Publication (Kokai) No. 09-261417 has a large size because the original is discharged to the original tray to re-circulate through the tray. Also, it is necessary to provide a memory with a large capacity for storing the results for all the originals in one circulating operation. Furthermore, when the original is jammed during the actual scan, or some of the originals are mistakenly removed from the original tray after completing the first determination scan (pre-scan), an order of the originals is changed and the apparatus uses incorrect results for the actual scan.
The apparatus disclosed in U.S. Pat. No. 5,946,527 employs the pre-scan/actual scan method, and uses the transport path for reading both sides of the original as described above. The apparatus determines a type of original when the original passes through the reading position for the first time (pre-scan) When the original is turned over front to back and passes through the reading position for the second time, the original is not read. When the original is switched back and passes through the reading position for the third time, the apparatus reads the original (actual scan) according to the determination result in the first reading. Therefore, it is necessary to turn over the original without reading it when the original passes through the reading position. Thus, it is difficult to read the color original at a high speed, thereby taking longer to read the original.
In view of the problems described above, the first object of the present invention is to provide an image reading apparatus and image reading method having a function for determining whether an original includes a black and white image and color image with one reading means without returning the original to a discharge tray, when reading a stack of originals containing both black and white originals and color image originals.
The second object of the present invention is to provide an image reading apparatus and image reading method with an improved overall reading speed for reading an original quickly according to a result of determination after determining whether the original is in black and white or contains color images without the original passing through the reading position and turning over.
The third object of the present invention is to provide an image reading apparatus and image reading method with an improved processing speed while preventing damage on an original. When an original is read up to a trailing edge thereof for determining whether the original is in black and white or contains color images, the original may be easy to bend or fold. In that case, when the original is determined to have a color image, the original is returned to a reading position, or the original is transported to a circulating path for turning over and is returned to the reading position according to a position the original.
Further objects and advantages of the invention will be apparent from the following description of the invention.